The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In general, intake air, which is introduced into a cylinder of an engine through an intake port, generates a tumble direction flow which rotates in a vertical direction in the cylinder, and a swirl direction flow which rotates in a horizontal direction in the cylinder.
In the related art, a large amount of intake air introduced into the cylinder flows in the swirl direction and is mixed with fuel injected through an injector so that combustion efficiency is improved.
In addition, in the case of a large-sized engine (e.g., an engine with a cylinder having a diameter of 100 mm or more) developed recently, the fuel may be injected at a high pressure by virtue of development of a fuel injection system. As the ultrahigh-pressure injection system is applied, the intake air introduced through the intake port rotates in the swirl direction, and we have discovered that the intake air hinders instantaneous combustion of atomized fuel particles by compression ignition.
The above information disclosed in this Background section is only for enhancement of understanding and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.